The moon phase display is a prized complication in horology.
However, known mechanisms do not take proper account of the correct display valid both in the Northern Hemisphere and the Southern Hemisphere. Indeed, the crescent visible in one hemisphere does not correspond to that of the other hemisphere, but to its mirror image. It is difficult to interpret a double moon correctly.
WO Patent 2011/113170, in the name of BVLGARI ROTH & GENTA, discloses a retrograde moon phase display mechanism with a double heart-shaped cam, each heart-piece corresponding to one of the moon cycles, so that the phase indicator wheel is moved in opposite directions during the waxing and waning moon phases.
EP Patent 2392976, in the name of AUDEMARS PIGUET, discloses a quite complex mechanism for a more detailed moon phase display than known mechanisms, which requires stacking discs on three levels and very special components, which, in the case of an enamelled dial and discs, requires new tools and the management of additional components. This mechanism can be adapted to either hemisphere through the use of particular discs, which are mounted when the watch is assembled, but it cannot instantaneously switch the moon phase display to match the vision from one hemisphere or the other.
U.S. Patent 2014/247699, in the name of TIMEX, discloses a known mechanism devised to simultaneously or selectively display moon phases in the Northern and/or Southern Hemisphere, for an electronic watch.